1. Field of the Invention
The present invention relates to an endoscope system, and in particular, relates to an endoscope system that can perform narrow band light observation.
2. Description of the Related Art
In a medical field, for example, surgeries using apparatuses such as endoscopes that are minimally invasive to living bodies have been performed. In addition, as observation methods using endoscopes, observation methods such as normal light observation and narrow band light observation have been known, the normal light observation being an observation in which an object in a living body is irradiated with light beams having individual colors of R (red), G (green), and B (blue) to obtain an image having coloring substantially similar to that by observation with the naked eye, and the narrow band light observation being an observation in which an object in a living body is irradiated with light beams having narrower bands as compared with the illumination light beams of the normal light observation to obtain an image in which blood vessels and the like existing in mucosal epithelium of a living body are accentuated.
Then, for example, Japanese Patent Application Laid-Open Publication No. 2005-6974 discloses an endoscope apparatus that includes a configuration capable of being switched into respective modes corresponding to the above-described two kinds of observation.
In contrast, in many endoscope apparatuses including one disclosed in Japanese Patent Application Laid-Open Publication No. 2005-6974, either of a frame-sequential or simultaneous image pickup scheme is employed.
More specifically, the above-described frame-sequential image pickup scheme can be implemented as, for example, a configuration in which an image pickup device, including no color filter provided on an image pickup surface, picks up an image of return light generated by irradiating an object with frame-sequential light that is obtained by time-dividing illumination light having a plurality of wavelength band components.
In addition, the above-described simultaneous image pickup scheme can be implemented as, for example, a configuration in which an image pickup device picks up an image of return light generated by irradiating an object with illumination light having a plurality of wavelength band components, the image pickup device including a color filter, provided on an image pickup surface thereof, in which a plurality of minute filters each having a predetermined spectral characteristic are disposed in a predetermined pattern.
Individual filters that are included in a color filter provided on the image pickup surface of the image pickup device are typically configured to have a spectral characteristic of transmitting not only light having a predetermined color component but also light having a broad band from a visible range to a near-infrared range.